Measurements and Laboratory Simulations of the Upper DNS Hierarchy 1 2 2 2 Duane Wessels , Marina Fomenkov , Nevil Brownlee , and kc claffy 1 The Measurement Factory, Inc.
[email protected] 2 CAIDA, San Diego Supercomputer Center, University of California, San Diego fmarina, nevil,
[email protected] Abstract. Given that the global DNS system, especially at the higher root and top-levels, experiences significant query loads, we seek to answer the following questions: (1) How does the choice of DNS caching software for local resolvers affect query load at the higher levels? (2) How do DNS caching implementations spread the query load among a set of higher level DNS servers? To answer these questions we did case studies of workday DNS traffic at the University of California San Diego (USA), the University of Auckland (New Zealand), and the University of Colorado at Boulder (USA). We also tested var- ious DNS caching implementations in fully controlled laboratory experiments. This paper presents the results of our analysis of real and simulated DNS traffic. We make recommendations to network administrators and software developers aimed at improving the overall DNS system. 1 Background The Domain Name System (DNS) is a fundamental component of the modern Inter- net [1], providing a critical link between human users and Internet routing infrastructure by mapping host names to IP addresses. The DNS hierarchical name space is divided into zones and coded in the widespread “dots” structure. For example, com is the parent zone for microsoft.com, cnn.com, and approximately 20 million other zones. The DNS hierarchy’s root zone is served by 13 nameservers, known collectively as the DNS root servers.